A recording apparatus has been known which has, as shown in FIG. 1, a recording laser 1 and a focusing laser 3. In operation of this recording apparatus, initial setting of optimum focusing position of a recording lens 21 is performed in accordance with the following procedure. As the first step, a head 19 is positioned at an optimum position by means of a head positioning mechanism 17, while a resist master disk 20 is not rotating. Then, the master disk 20 is driven to rotate at a predetermined speed and, when the disk rotation has become steady at that speed, the recording laser 1 is activated so that recording laser light is made to be incident to the master disk 20 via mirrors 5, 7 and 9 and then through a recording lens 21. The laser light reflected by the master disk 20 runs backward along the same optical path as the incident light so as to impinge upon a CCD camera 13 from the mirror 5, whereby a laser spot image is formed on the monitor 15 through the camera 13. The operator, while visually observing the state of the laser spot image, controls a motor driver 29 so as to control a motor 27 thereby moving a photo-detector (PD) to the left and right. A servo circuit 31 performs a fine control of the position of the recording lens in the up and down directions so as to position the recording lens 21 at such a position that the above-mentioned laser light impinges upon the center of the PD 23 which is set at a position as a result of the above-mentioned control performed by the operator. This operation is repeated so that the recording lens 21 is set at the optimum focusing position.
In the above-described operation for initially setting the recording lens 21 at the optimum position, the laser spot image of the recording laser light displayed on the monitor 15 linearly changes in accordance with the movement of the PD 23, because the laser spot light is analog information. Considerably high degrees of skill and experience, therefore, are required in order to adequately position the recording lens 21 by visually finding the laser spot image corresponding to the optimum focusing position of the recording lens 21 through continuous visual chasing of the change in the laser spot image. The optimum focusing position of the recording lens 21 delicately varies according to the type of the resist master disk. Therefore, the above-described work is considerably troublesome even for skilled and experienced operators. Thus, it is not easy to position the recording lens 21 with a high degree of accuracy.
The described recording apparatus suffers from another disadvantage in that, even if the recording lens 21 has been set at the optimum focusing position, the data indicative of such optimum focusing position cannot be relied upon for the purpose of reproduction of the optimum focusing position, because the data is analog data which is in the form of the laser spot image displayed on the monitor 15 and cannot be stored.
Consequently, the above-described troublesome work is necessarily conducted each time the type of the resist master disk is changed, thus impairing the efficiency of the whole process.
Accordingly, an object of the present invention is to provide a recording apparatus in which the data indicative of the optimum focusing position of the recording lens is changed into numerical values so as to facilitate the work for initially setting the optimum focusing position of the recording lens for each type of resist master disk.